Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in molecular systems. In Raman spectroscopy, an approximately monochromatic beam of light of a particular wavelength range passes through a sample of molecules and a spectrum of scattered light is emitted. The spectrum of wavelengths emitted from the molecule is called a “Raman spectrum” and the emitted light is called “Raman scattered light.” A Raman spectrum can reveal electronic, vibrational, and rotational energy levels of a molecule. Different molecules produce different Raman spectrums that can be used like a fingerprint to identify molecules and even determine the structure of the molecules.
The Raman scattered light generated by a compound (or ion) adsorbed on or within a few nanometers of a structured metal surface can be exponentially greater than the Raman scattered light generated by the same compound in a solution or in a gas phase. This process of analyzing a compound is called Surface Enhanced Raman Spectroscopy (SERS).
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